Control apparatus



Patented Dec. 31 1940 UNITED STATES CONTROL APPARATUS Eldon D. Raney, Columbus, Ohio, assignor to Banco Incorporated, Columbus, Ohio, a corporation of Qhio Application April 23, 1938, Serial No. 203,887

g 4 Claims. (Cl. 15828) The present invention relates to control systems for oil burning apparatus and more particularly to automatic controls for preventing injection of ignitible fuel into the furnace except when ignition is present and only after a predetermined purging time has elapsed after the previous cessation of injection of fuel.

One of the objects of the present invention is to provide an improved control system for a fuel A burning apparatus in which the circuit, utilized for starting the apparatus, is rendered ineffective after such starting and it is not reconditioned to restart the apparatus until a predetermined time has elapsed after the cessation of operation of the apparatus.

Another object of the present invention is to provide an improved control system for a fuel burning apparatus in which the first circuit to be energized, in response to a demand for heat from the apparatus, is the secondary circuit of a transformer, the primary circuit of such transformer being controlled by a time delay device and not being in a condition to be energized until a prep determined time after the previous cessation of operation of the apparatus, the said primary circuit being rendered ineffective, by the delay device, substantially immediately after the starting circuit is established for maintaining the transformer operative.

Other and-further objects and advantages will be apparent from the following description, reference being had to the accompanying drawing wherein preferred forms of embodiments of the present invention are clearly shown.

In the drawing:

Fig. 1 is a diagrammatical view of one embodim ment of the invention, and,

Figs. 2 and 3 are fragmentary diagrammatical views, each showing a different embodiment of the invention.

Referring to the drawing the means which controls the flow of fluid is herein shown as a motor which may be utilized for actuating a fuel pump and an air fan of the fuel burning apparatus. The motor 20 is controlled by a switch 2| and the circuit therefor includes high voltage line 22, wire 23, motor 29, wire 25, stationary contacts 26 and 21 of switch 2|, which contacts are bridged by an electro magnetically operated contact 28, wire 3|), heating coil 3| of time delay device 32, wire 35, stationary contacts 31 and 38 of a safety switch 39, which contacts are bridged by a movable contact 49, and the other main line 4|.

Switch 2| is closed when the electro magnet coil 43 thereof is energized. The circuit for wind ing 43 includes secondary winding 44 of transformer 45, wire 46, winding 43, wire 48, movable contact 49 of room thermostat 59, contact 5| and wire 53. The safety switch 39 normally is closed, and, when the starting switch 2| is closed by room 1 thermostat 56, current will be supplied to the motor 20. Switch 2| also controls the ignition for the fuel. Any type of ignition may be provided and that herein shown is the high voltage type including primary winding 55 and the secondary 5 high voltage winding 56, the spark gap being indicated at 51. The inition is connected in parallel with the motor, the parallel circuit including a wire 59 connected with wire 23, stationary contact 60 of i'gnition switch 6|, movable contact 62, 2 wire63, winding 55 and wire 64, which latter is connected with wire 25;

It will of course be understood that the secondary circuit of the transformer will not be energized unless the primary coil 66 of transformer 45 is energized. The circuit for coil 66 includes line 22, wire 61, winding 66, wire 68, a stationary contact 69 of time delay device 32, a movable bimetallic strip 1| of time delay device 32, which strip is anchored at 12, wire 13, heating coil 3|, 30 wire 35, safety switch 39 and line 4|. Whenever strip 1| engages contact 69, current is supplied to the transformer whereby the motor can be started upon demand by the room thermostat 50.

If'the heating-coil 3| is in series only with coil 66 of transfprmer45, the heat generated by coil 3| is not sufficient to flex bimetal 1| from contact 69 due to the resistance offered by coil 66. However, when the heating coil 3| is in series with the motor 20, sufiicient heat will be generated in 4 coil 3| to cause thermostat 1| to flex away from contact 69 but this flexing will be gradual and will occur after a second transformer circuit is completed. This second transformer circuit includes line 22, wire 61, winding 66, wire 15, a

contact 2? of starting switch 2|, which is now engaging contact 21, 'wire 3|], coil 3|, wire 35, safety switch 39 and line 4|. Thus it is apparent that energization of primary transformer winding 66 is maintained after thermostatic strip 1| 5 separates from contact 69 and the second transformer primary circuit will be maintained as long. as coil 43 of the secondary circuit is energized.

When the coil 43 is deenergized, either by the room thermostat 58 or power failure of any type, the armature operated contact 28 of starting switch 2| will be separated from contact. 26 and 21, to thereby interrupt the circuit to the motor and the second primary transformer circuit including wire 15. Although there is a reoccurring demand for heat by the thermostat, or in the event of reestablishment of a previous cessation of electrical energy, the motor 28 cannot be started until a predetermined time has elapsed after the previous cessation of operation thereof. This is apparent because the first primary circuit for the transformer is interrupted at 1| and 69 and the second transformer circuit is interrupted at 28 and 21. At this time no current is -fiowing in coil 3| of time delay device 32 and 1 therefore bimetallic strip 1| is cold or is cooling.

. from contacts 31 and 38.

After a predetermined time, strip 1| will reengage contact 69 to thus reestablish the first primary transformer circuit. The time. interval between the cessation of operation of the motor and the .recondition, of the first primary circuit of the transformer, by reengagement of strip 1| with contact 69, is sufficient to permit purging of nonspent gasses from the furnace chamber.

In the event that the fuel does not ignite, during starting of the apparatus or in the event of flame failure during the operation of the motor 28, the motor 28 is rendered inoperative by the separation of contact 48, of safety switch 39, The safety switch 39 includes a lever I6 pivoted at 11 on a stationary bracket 18. This lever is normally biased to hold the contacts closed by a spring 19 but when the lever 16 is thrown past its dead center position, with respect to the spring 19 and pivot 11, the lever 18 will be biased to open the contacts of the switch, and the lever must be reset manually. The lever 16 is adapted to be actuated by a lever 8| of snap acting mechanism 82. This snap acting mechanism includes a lever 83 and, like lever 8|, is pivoted at 84 on the bracket 82. A spring 85 biases the levers BI and 83 either in one direction .or the other. In the present illustration the lever 83 is moved upwardly by a bimetallic strip 81 when the strip is heated. Continuous upward movement of the strip 81 causes the lever to move beyond its dead center position, with respect to the spring 85 and lever 8|, whereby lever 8| will be moved upwardly. During normal operation, that is when heat is generated by the fuel burning apparatus, the upward movement of lever 8| is limited by a combustion responsive controller 88. This controller includes a thermostat 89 anchored at 98 and is responsive to heat of combustion. The

lower part of thermostat 89 is adapted to move to the right when combustion takes place to move a stop 9| in the path of the lever 8|. The

stop 9| is operated through the usual type of substantially immediately upon change of temperature of thermostat 89. In the event of failure of ignition of the fuel, during starting, the

. stop 9| will not stop the upward, movement of lever 8| and a leg 95 of lever 8| will engage a leg 96 of lever 16 and will lift the lever 18 beyond its deadcenter position to thereby open the safety switch 39.

The thermostatic strip 81 of the snap acting mechanism 82 is heated by an electricheater 98.

The circuit for this heater includes line 22, wire 61, wire 99, coil 98, strip 81, contact I88 carried by lever-83, wire I8I, wire 25, contacts 26, 28 and 21, wire 38, heater 3|, wire 35, safety switch 39 and line 8|. Thus it is apparent that when the starting switch 2|- is closed, coil 98 is energlzed and will, after a predetermined time, operate the snap acting mechanism 82. The time interval from the starting of heating of the coil 98 until the time when the snap mechanism 82 moves upwardly through its dead center position is sufficient for normal starting of the fuel burning apparatus so that in the event of failure of ignition the safety switch will be operated to interrupt the initial circuit of the system.

In the event it is desirable to provide ignition during the starting period only, the ignition circuit may be interrupted, as shown, by the snap mechanism 82, that is the contact 62 of the ignition circuit is carried by the lever 8|.

In the embodiment shown in Fig. 1 the contact I88 is separated from thermostatic strip 81 when the lever 83 is toggled upwardly through dead center whereby the circuit to the heating shown as carrying a rod I83 which falls by gravity and is assisted by a spring I84. This rod I83 carries a pin I85 arranged to engage the 'upper side of lever 83 and move the lever 83 downwardly when the armature 28 falls out.

The pin I85 will be lifted to its upper position when the armature is attached and may function as a stop for limiting the upward movement of the lever 83. The position of stop 9| of combustion control 88, when in stopping position for lever 8|, is such that the lever 8| will also be snapped downwardly when the armature 28 falls out, so that ignition is insured for the succeeding restarting of the system. The downward movements of lever 83 and 8| are limited by a stop I86 and contact 68, respectively.

In the event of flame failure after ignition has taken place, the cooling of the thermostat 89 will cause the stop 9| to move to the right and slide off of the edge of lever 8|. The snap acting mechanism 82 being biased upwardly will cause the lever 8| to move further upwardly which in turn will cause leg toengage leg 96 and thereby snap lever 16 to the circuit opening position. The safety switch'39 must be re set manually. Thus it is apparent that the snap acting mechanism for the safety switch is biased at all times after the starting operation toward a safety switch opening position and that the safety switch is prevented from operating only by the combustion control. Therefore, as soon as there is a failure of fuel, the safety switch is open at the instant that the temperature of the thermostat 89 recedes. Thus quick operation of the safety switch is assured.

It is desirable to limit the heating of coil 3| and strip 1| of the time delay device 82. This is accomplished by shunting the current through contact I81 on strip 1|, stationary contact I88 and wire I89 connected with wire 35. it-

will be seen that when contact I81 engages contact I88, the heating, coil 8| will be either short circuited or part of current will be shunted through wire I89. As soon as, the coil 3| and strip 1| cools slightly contact I81 will separate from contact I88 to interrupt the shunt. It will of course'be understood that at no time will strip ll be cooled to sucha degree as to engage contact 69 except when contact 28 is separated from contacts 25 and 21.

The present illustration includes a differential type room thermostat in which the bimetal III thereof is. pivoted at H2 and the temperature at which the same operates is governed by a hand adjusting cam II3. Upon cooling of the room containing the thermostat, the right arm of thermostatic strip III moves to the left and first engages spring contact 49 which'is anchored at H4 and then causes contact 49 to engage contact 5I to complete the. circuit of the secondary transformer traced above. As the room temperature increases, the right hand arm of strip III moves to the right and the contact 49, normally biased to the right, follows the right arm of strip -I I I. A circuit, however, is maintained through the coil 43 after strip III moves far enough to permit contact 49 to separate from contact 5|. This circuit includes coil 44, wire 46, winding 43, wire 48, .contact 49, strip III, wire II5 contact IIB, which contact is closed on contact I II when armature 28 is attracted, contact III and wires I I8 and 53. This holding circuit is maintained as long as the armature 28 is raised and until the room thermostat 50 is heated sufficiently to cause strip III to separate from contact 49. The point at whichstrip III separates from 49 is governed by an adjustable screw I20 which in effect provides a control of the differential between between the opening and closing of the circuit of the starting switch coil 43.

If desirable the heating coil 98 of thefsafety switch actuating mechanism may be maintained energized throughout the period when the motor 20 is operative. In that case it can be conn ected as shown in Fig. 2 wherein'wire IOI is directly connected to the coil 98. In this view the snap mechanism 82 is shown in the position which it assumes after it is snap actuated. In this embodiment the biasof spring I04 and the weight of the armature 28 and rod I03 and the other parts carried thereby is sufficient to overcome the bias of not only'the spring 85 but also the tension of thermostatic strip 81, when thearmature is released by the coil 43. It will be noted that the only function to be performed by the current induced into the secondary winding 44 is to energize coil 43. Therefore, sufiicient current is available in coil 43 to lift a relatively heavy armature.

- It may be desirable to limit the temperature of heating coil 98, in such case the construction may be like that shown in Fig. 3 in which the thermostatic strip 81 is pivotally mounted at I20 and carries a contact I2I which engages the contact I22. The circuit for the heating coil includes the contacts I22 and I2I and the wire IOI is connected to the pivot I20. When the thermostatic strip 81 is heated the arms I24 and I25 tend to spread but the spring 428 under arm I25 restrains the movement of arm I25 sumciently so that arm I24 moves first and after it snaps the switch mechanism 82 through center, the upward movementof arm I24 is stopped by lever 83. Further movement of the strip 8'!v will be a downward against contact I22 to again complete the circuit through coil 98. v

The making and breaking of the heater coil 98 of the snap acting mechanism of the safety switch 39 is made possible by devising a circuit in which the heating coil 98 is connected in parallel with the motor and the primary winding 68 of transformer 45 and the arranging of this parallel circuit so that it is capable of being energized only when the motor is energized.

While the forms of embodiments of the present invention as herein disclosed constitutes preferred forms, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow:

1. A fuel burner control system comprising in combination, a transformer including a primary winding and a secondary-winding; a circuit for energizing the primary winding; a thermally actuated time switch in the circuit, said switch being adapted to open the circuit when heated to 'a predetermined temperature; a second circuit for energizing the primary winding; an electrically operated fuel feeding device, said device having a greater current capacity than said primary winding; a circuit for energizing said device; means energized by the secondary winding for closing said second circuit and the last mentioned circuit; and electric heating means in series with the aforementioned circuits, said heating means being adapted to heat said thermal switch to said predetermined temperature when the fuel feeding device is energized.

2. A fuel burning control system comprising in combination with a source of current, a relay; electrically operated fuel feeding mechanism and a heating element connected in seriescircuit relation and connected to said source of current by trically operated ralay; two controlling circuits for the relay; a switch in one of said two circuits, and the other of said circuits being closed .by the relay; a thermal device for opening the said switch at a predetermined temperature thereof; an electric heater for heating the thermal device, said heater being connected in both of said circuits; and an electrically operated fuel feeding device, said relay being adapted. to connect the fuel feeding device and the heater in series circuit relation and with the source of current, the resistance of said one circuit limiting the flow of current to a value insufflcient to heat the thermal device to said predetermined temperature, and the current in the fuel feeding device energizing the heater to heat the thermal device above said predetermined temperature.

4. A fuel burner control system comprising in combination with a source of current, an electrically operated relay; two controlling circuits for the relay; a switch in one of said two circuits, and the other of said circuits being closed by the relay; a thermal device for opening the said switch at a. predetermined temperature thereof; an electric heater for heating the thermal device, said heater being connected in both of said circuits; an electrically operated fuel feeding device, said relay being adapted to connect the fuel feeding device and the heater in series circuit relation and with the source of current, the resistance of said one circuit limiting the flow of current to a value insufiiclent to heat the ther- 5 mal device to said predetermined temperature,

and the current in the fuel feeding device energizing the heater to heat the thermal device above 

